Medical imaging has recently expanded into the dual- or multi-modality fusion of anatomical and functional imaging modalities. This significantly improves the diagnostic power while simultaneously increasing the cost of an already expensive medical devices or investigations and decreasing their mobility. We are introducing a novel imaging concept of four-dimensional (4D) Microwave Tomographic (MWT) functional imaging: three-dimensional (3D) in spatial domain plus one-dimension (1D) in the time, functional dynamic domain. Instead of a fusion of images obtained by different imaging modalities, 4D MWT fuses absolute anatomical images with dynamic, differential images of the same imaging technology. The approach was successively validated in animal experiments with short term arterial flow reduction and a simulated compartment syndrome in an initial simplified experimental setting using dedicated microwave tomographic system. The presented fused images are not perfect as MWT is a novel imaging modality at its early stage of the development and ways of reading of reconstructed MWT images need to be further studied and understood. However, the reconstructed fused images present clear evidence that microwave tomography is an emerging imaging modality with great potentials for functional imaging.

Microwave Tomography (MWT) is a novel imaging modality which might be applicable for non-invasive assessment of functional and pathological conditions of biological tissues. The imaging of the soft tissue of extremities is one of its potential applications. The feasibility of this technology for such applications was demonstrated earlier. This is the first of two companion papers focused on an application of MWT for imaging of the extremity’s soft tissues. The goal of this study is to assess the technical performance of the developed 2D MWT system dedicated for imaging of functional and pathological conditions of the extremity’s soft tissues. Specifically, the system’s performance was tested by its ability to detect signals associated with physiological activity and soft tissue interventions (circulatory related changes, blood flow reduction and a simulated compartmental syndrome) – so called “physiological signatures”. The developed 2D MWT system dedicated for an imaging of animal extremities demonstrates good technical performance allowing for stable and predictable data acquisition with reasonable agreement between experimentally measured electromagnetic (EM) field and simulated EM field within a measurement domain. Using the system we were able to obtain physiological signatures associated with systolic vs diastolic phases of circulation in an animal extremity, reperfusion vs occlusion phases of the blood supply to the animal’s extremity and the a compartment syndrome. The imaging results are presented and discussed in the second companion paper.

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The effect of an extended flexor carpi radialis approach on the blood supply of the radius was examined in six (3 paired) fresh frozen cadaver limbs after injection with India ink and clearing using a modified Spalteholz technique. An extended flexor carpi radialis approach to the distal radius was made in the left limb in each of the three-paired limbs. The right limb served as a nonoperative control. Following perfusion of the arterial vasculatureof each limb with India ink, serial transverse sections were cut and the intraosseous blood supply evaluated using a modified Spalteholz technique. Both controls and surgical specimens demonstrated compíete cortical penetration from endosteal vessels in the proximal and midsectionsof the radius. In the distal radius, surgical specimens demonstrated reduced perfusion volarly, however there continued to be perfusion of ink through intact dorsal and ulnar metaphyseal perforating arteries. Persistent vascular perfusion to the distal radius remains through intact endosteal vessels and metaphyseal perforators of extensive surgical soft-tissue stripping.

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